Recent clinical and epidemiological studies have defined the presence of individuals with natural immunity to infection with filarial parasites. Some infected individuals may remain microfilaremic over long periods of time, without developing overt lymphatic pathology, but others develop such pathology that can develop either in the setting of persistent microfilaremia or after microfilaremia has cleared. The underlying mechanisms for these differences are being assessed at the genetic and immunologic level. PCR-based amplifications of parasite DNA in skin snips from patients with onchocerciasis have increased diagnostic sensitivity and specificity, and the assays have been configured into an ELISA format that is field applicable. Efforts to acheive detection DNA in lymphatic filariasis and in loiasis have also been developed and placed into field applicable formats. Adverse reactions associated with treatment of onchocerciasis and lymphatic filariasis have been shown to be mediated by proinflammatory cytokines (IL-6 and TNF-a), the growth factors IL-5 and GM-CSF, and the eosinophil chemoattractant, RANTES. Albendazole, an anthelmintic drug with primarily macrofilaricidal effects, has been shown capable of successfully treating loiasis refractory to standard therapy.